Oy -- I just got reminded of another dream, in which I had apparently ordered a CD of R&H's ALLEGRO from someone selling through Amazon, and when it arrived I found that I'd already purchased it at a store.
Buying things twice by mistake happens to me rather too often in real life 
Oh, ain't it the truth! I've "re-bought" DVDs, Blu rays and CDs. It's so very annoying to find I already had it.
Of course I do this in wide awake real life, too. Mostly in the DVD department. Current case in point: I guess some months ago I picked up the DVD of PANIC IN THE STREETS along with a handful of other items, put it on the shelf, and hadn't yet gotten around to watching it. Then a couple of weeks ago, I saw a nice secondhand copy of it in an FYE store and said Wow! I'll take that! I get home, find its place on the shelf, and ..... oh my. So one copy goes in the sell-back-or-giveaway stack. Not three days later, to add one final kick in the arse, I see the press release announcing a must-have Blu-ray transfer.
Oh, and this is why one keeps a "database" of one's collection, right? It would have been available via the smartphone had I bothered to check it in the store -- but there's a flaw in the system if you don't check every single thing. I didn't check, just in case, because I truly didn't recognize it as something I even MIGHT have already had. Oy!